Interference is becoming a serious threat for current Global Navigation Satellite System (GNSS) receivers. One of the more serious threats is the ever increasing number of personal GNSS jammers used by people to block the possibility of monitoring their movements using GNSS receivers. The careless use of personal GNSS jammers can cause serious problems for airborne GNSS receivers. In addition, spoofing methods are used to trick GNSS receivers into producing false information. Spoofing can be used to steer ships off course or bring down aircraft. These types of attacks will likely become more common as GNSS receivers are more heavily relied on to provide users with accurate and reliable positioning and velocity information.